Hot reload, rebuild and update simulator on file changes

dev.sh

#!/usr/bin/env bash

set -uo pipefail

WATCH_PATH="<PROJECT_PATH>"
RUN_SCRIPT="./run-simulator.sh"

log() {
    printf '[dev %s] %s\n' "$(date '+%H:%M:%S')" "$1"
}

if ! command -v fswatch >/dev/null 2>&1; then
    log "Error: fswatch is not installed or is not on PATH."
    exit 1
fi

if [[ ! -x "$RUN_SCRIPT" ]]; then
    log "Error: $RUN_SCRIPT is missing or is not executable."
    exit 1
fi

trap 'log "Watcher stopped."; exit 0' INT TERM

log "Watching $WATCH_PATH for source changes."
log "Press Ctrl+C to stop."

fswatch -o "$WATCH_PATH" |
    while read -r event_count; do
        log "Detected $event_count filesystem change event(s). Rebuilding…"

        if "$RUN_SCRIPT"; then
            log "Update completed. Waiting for more changes."
        else
            log "Update failed. Fix the error and save a file to retry."
        fi
    done

run-simulator.sh

#!/usr/bin/env bash

set -uo pipefail

PROJECT="<PROJECT_NAME>.xcodeproj"
SCHEME="<SCHEME_NAME>"
DERIVED_DATA_PATH=".build"
APP_PATH="$DERIVED_DATA_PATH/Build/Products/Debug-iphonesimulator/<FILE_NAME>.app"
BUNDLE_ID="<BUNDLE_ID>"

log() {
    printf '[simulator %s] %s\n' "$(date '+%H:%M:%S')" "$1"
}

log "Checking for a booted simulator…"
if ! xcrun simctl list devices booted; then
    log "Error: unable to communicate with Simulator."
    exit 1
fi

log "Building scheme '$SCHEME' from $PROJECT ..."
if ! xcodebuild \
    -project "$PROJECT" \
    -scheme "$SCHEME" \
    -configuration Debug \
    -destination 'generic/platform=iOS Simulator' \
    -derivedDataPath "$DERIVED_DATA_PATH" \
    build; then
    log "Build failed. The app was not installed."
    exit 1
fi

if [[ ! -d "$APP_PATH" ]]; then
    log "Error: build succeeded, but the app was not found at $APP_PATH."
    exit 1
fi

log "Build succeeded. Installing $APP_PATH ..."
if ! xcrun simctl install booted "$APP_PATH"; then
    log "Installation failed. Confirm that a compatible simulator is booted."
    exit 1
fi

log "Installation succeeded. Launching $BUNDLE_ID ..."
if ! xcrun simctl launch --terminate-running-process booted "$BUNDLE_ID"; then
    log "Launch failed."
    exit 1
fi

log "App launched successfully."